An optical parametric oscillator has been formerly used as the multiple wavelength laser device using light excitation. However, it is necessary to mechanically adjust a laser incident angle to a nonlinear crystal so as to realize a multiple wavelength. Therefore, there is a problem in points of high speed formation and reproducibility of the wavelength. Further, a problem exists in that an optical system of many stages is required, and the device is large-sized. In contrast to this, for example, JP-A-2003-243754 and JP-A-2002-151774 (corresponding to U.S. Pat. No. 6,636,537) are disclosed.
A multiple wavelength laser device shown in JP-A-2003-243754 is set to a construction in which Yb and Nd are added to a laser base material as rare earth ions, and plural lights of different wavelengths emitted from ion elements are selectively laser-oscillated by a multiple wavelength selecting element. A multiple wavelength laser device shown in U.S. Pat. No. 6,636,537 is formed by constructing a resonant optical system different every wavelength.
Further, JP-A-2005-20002 (corresponding to U.S. Pat. No. 6,879,618) discloses a construction in which an organic active layer constituting a vertical laser resonator is excited by incoherent light outputted from an organic light emitting diode as an excitation light source, and is resonated by a reflecting mirror and a laser beam is outputted. The organic active layer includes organic molecules of a host and a dopant, and the incoherent light is absorbed by a host material. Thereafter, excitation energy can be moved to the dopant by a Foerster type energy movement. Namely, the laser beam having a wavelength proper to the dopant is outputted.
Transition probability of rare earth is different in each element, and is also different in accordance with an energy level even within the same element. Further, the reflectivity of the reflecting mirror constituting the resonator has wavelength dependence property. Accordingly, in the construction shown in JP-A-2003-243754, when the resonances of plural lights of different wavelengths are simultaneously executed, it is difficult to set light emitting intensity of each wavelength to the same. For example, when the multiple wavelength laser device is set to an RGB light source for display, it is considered that polarization is caused in color. Further, since light sources for exciting Yb and Nd are individually required, it is difficult to make the device compact.
In the case of the construction shown in U.S. Pat. No. 6,636,537, as mentioned above, since the resonant optical system different every wavelength is required, it is difficult to make the device compact.
Further, in the construction shown in U.S. Pat. No. 6,879,618, when it is considered that the resonances of plural lights of different wavelengths are simultaneously executed, it is necessary to select a host material and a dopant material suitable for each wavelength. Further, the excitation light source is required every each wavelength. Accordingly, it is difficult to make the device compact. Further, after the incoherent light is absorbed by the host material, excitation energy is moved to the dopant and light is emitted. Therefore, a problem exists in that conversion efficiency to the laser beam is low.